Grounding receptacle



Feb. 13, 1968 J. A. SUNDQUIST GROUNDING RECEPTACLE Filed May 12, 1966 NMummy INVENTOR.

United States Patent 3,369,211 GROUNDING REQEPTACLE John A. Sundquist,Trumbull, Conn, assignor to Harvey Hubbell, Incorporated, Bridgeport,Conn., a corporation of Connecticut Filed May 12, 1966, Ser. No. 549,70510 Claims. (Cl. 339-14) This invention relates to a grounding electricalreceptacle and, more particularly, to such a receptacle wherein thegrounding elements are isolated from the mounting strap.

A common type of receptacle which is widely used in electrical wiringincludes a pair of slots and associated female contacts for receivingthe line blades of a male plug and a third semi-circular openingassociated with the female grounding contact for receiving a groundingprong on the plug. In receptacles of this type, it is customary to mountthe female grounding contact on the metallic mounting strap whichencircles the rear portion of the receptacle and is used formechanically mounting the receptacle in an outlet box. The groundingconnection is thus made through the outlet box and the metallic sheathedcable, or conduit, to a water pipe.

In certain electronic and communication installations, such a systemground often introduces unwanted interference which creates noise ordistortion in sensitive apparatus. In these installations a separategrounding Wire is required and this often necessitates the use ofspecially designed receptacles, outlets, boxes, or plates.

Accordingly, it is a primary object of the present invention to providean improved grounding receptacle. Other objects are to provide such areceptacle wherein the grounding contacts are electrically isolated fromthe mounting strap; wherein a separate grounding connection may be madeto the grounding contact; and wherein the receptacle may be mounted in astandard outlet box and covered by a standard plate.

The manner in which the foregoing objects are achieved will be apparentfrom the following description, the appended claims and the figures ofthe attached drawing wherein:

FIG. 1 is a back view, partially broken away, of a duplex receptacleconstructed in accordance with the present invention;

FIG. 2 is a right side view of the receptacle of FIG. 1, partiallybroken away to illustrate its internal construction;

FIG. 3 is a perspective view illustrating the construction of the groundcontacts of the receptacle of FIGS. 1 and 2;

FIG. 4 is a back view, partially broken away, of a single receptacleconstructed in accordance with the present invention;

FIG. 5 is a left side view of the receptacle of FIG. 4, partially brokenaway to illustrate its internal construction; and

FIG. 6 is a perspective view illustrating the construction of thegrounding contact of the receptacle of FIGS. 4 and 5.

The objects of the present invention are achieved by means of anelectrical grounding receptacle which comprises a body of insulatingmaterial defining chambers therein. The body includes a face portionwhich defines openings communicating with the chambers. A plurality offemale electrical contacts are positioned Within the chambers and arealigned to receive male contacts inserted through the openings. Agrounding terminal is mounted on the body and an electrical conductorjoins the grounding terminal and at least one of the female electricalcontacts. A metallic mounting strap is provided on the body andinsulating means isolate the conductor from the mounting strap.

With particular reference to FIGS. l-3, there is illustrated a duplexreceptacle comprising a body 10 of the usual insulating material. On itsfront surface the body 10 is provided with faces 12, 14 for receivingthe two line blades and the grounding prong of a male plug P.Intermediate the faces, a circular hole 15 extends through body 10. Thegrounding opening 16 of the upper face and the similar opening 18 of thelower face are illustrated inFIG. 2. Each of these openings communicateswith an internal chamber, such as chamber 20 communieating withgrounding opening 16, and chamber 21 communicating with groundingopening 18. These chambers extend completely through the body 10. Theback of body 10 is closed by means of an insulating back plate 22. Theback plate 22 includes the usual back wiring openings 24 and is providedwith a groove 25 of rectangular cross section which extendslongitudinally along the entire length of the back surface. Arectangular opening 26 within the groove 25 is aligned with chamber 20and a circular opening 27 is aligned with hole 15. At its lower righthand corner, as seen in FIG. 1, the back plate 22 is cut away to form anotch 28, which extends into alignment with the chamber 21. A passage 30in the side Wall of body 10 extends from the rear surface of the bodyand communicates with the chamber 21. In addition, the side Wall isprovided with a recess 32 for receiving the wiring terminal plate, aswill be later disclosed.

Housed within chamber 20 is a U-shaped spring grounding contact 34 andwithin chamber 21 is a U- shaped spring grounding contact 36. Inreceptacles constructed in accordance with the prior art, the groundingcontacts are riveted directly to the mounting strap. However, in thepresent construction they are riveted to the end of an electricallyconductive bridging member 38 which is shown in detail in FIG. 3.

The bridging member 38 is substantially L-shaped, the leg 40 of the Lterminating in a Wiring terminal plate 42 which is bent downwardly asshown. The terminal plate 42 is drilled and tapped to receive a bindingscrew 44. Extending from the terminal plate 42 is a locking lug 46 andan outwardly bent conductor retaining tab 48. The main body of thebridging'member 38 is provided with an enlarged portion 50 which definesan opening 52 which is larger than the opening 27 in the back plate 22.The grounding contacts 34, 36 on bridging member 38 are inserted,respectively, through the opening 26 and notch 28 in the back plate intothe chambers 20, 21. The terminal plate 42 slides Within the recess 32on the side of the body 10 and the locking lug 46 enters a lockingopening formed in the body adjacent the recess 32. When fully inserted,the main body portion of the bridging member 38 is positioned within therecess 25 with its large opening 52 concentric with the smaller opening27 in the back plate.

Mounted against the bridging member 38 and also contained within thegroove 25 is a rectangular insulating strip 54. The insulating stripdefines a circular opening 56 of substantially the same size as theopening 27 in the back plate but considerably smaller than the opening52 in the bridging member with which it is aligned.

The U-shaped metal mounting strap 58 is next mounted within the recess25 and against the insulating strip 54. The mounting strap extendsaround the ends of the body 10 Where it is retained by molded lockinglugs in the usual manner and includes an opening 6t] aligned with thehole 15 of the body It} and flanked by a pair of raised bosses 62. Abushing 64 is inserted through the opening 60 in the mounting strap andinto the hole 15 in body 19. This bushing is drilled and tapped at oneend and includes a square head 66 at the other end which is positionedbetween the bosses 62 to resist rotation. A screw 68 extends into thedrilled and tapped end of bushing 64 between the faces 12, 14 on thefront of the receptacle and may be used to secure the cover plate.

It will now be seen that the receptacle of FIGS. 1-3 provides a novelconstruction for receiving the threeprong grounding plugs commonly inuse. However, the female grounding contacts are completely isolatedelectrically from the mounting strap by reason of the insulating strip54 and the clearance between opening 52 and bushing 64. The contacts maybe grounded only by a separate grounding conductor connected to bindingscrew In FIGS. 4-6 there is illustrated a modification of the inventionas applied to a single receptacle. In this modification the body 70 isapproximately cubic and has a single face 72 which defines a groundingopening 74 communicating with a chamber 76. A hole 78 extends throughthe body 79 from front to back. The corners of the body 70 are mitered,as seen in FIG. 4, but the lower left hand corner is cut away even moreso as to define a recess 80 in the rearward portion of the body 76.

The back of the body 70 is closed by a back plate 82 which includes theusual wiring openings 84. It also defines a groove 36 which extendslongitudinally of the base plate from top to bottom as seen in FIG. 4.In addition the back plate also defines an auxiliary groove 88 whichextends diagonally from the main groove to the recess 80. Within thegroove 86 there is a rectangular opening 90 which communicates with thechamber 76 and a central opening 92 aligned with, and of substantiallythe same size as, hole 78.

An angled ground strap 94 is mounted within the groove 86 and supports agrounding contact 96 which is riveted thereto and positioned within thechamber 76. The ground strap 94 defines an enlarged opening 98concentric with, but larger than, the opening 92. The angled end of theground strap is bent downwardly to form a wiring terminal plate 100which is positioned within the recess 80. The terminal plate is drilledand tapped to receive a binding screw 102. The body 70 is apertured toprovide clearance for the end of screw 102.

Also mounted within the groove 86 and auxiliary groove 88 and atop theground strap 94 is an insulating strip 104. As seen in FIG. 6, thisstrip has a shape similar to that of the ground strap 94 and defines anopening 106 which is aligned with, but smaller than, the opening 98. Themetal mounting strap 108 is mounted within the groove 86 and against themajor portion of the insulating strip 104. The mounting strap extendsaround the top and bottom of the body in the usual manner and the entireassembly is held together by means of a bolt 1163 extending through thehole 78 and the various aligned openings and retained by a nut 112. Itwill thus be seen that, in a manner similar to that of the duplexreceptacle, the grounding contact 96 is completely isolated from themounting strap 108, the sole connection thereto being made by means ofbinding screw 102. It will also be obvious that bolt 110 and nut 112 maybe replaced by a rivet.

It is believed that the many advantages of this invention will now beapparent to those skilled in the art. It is also believed that manyvariations and modifications will be apparent which do not depart fromthe spirit and scope of the invention. Accordingly, the foregoingdescription is to be construed as illustrative only, rather thanlimiting. This invention is limited only by the scope of the followingclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electrical grounding receptacle which comprises: a body ofinsulating material defining chambers therein and including a faceportion defining openings communicating with said chambers; a pluralityof female electrical cont-acts within said chambers aligned to receivemale contacts inserted through said openings; grounding terminal meanson said body; an electrical conductor joining said grounding terminalmeans and at least one of said female electrical contacts; a metallicmounting strap on said body; and insulating means for electricallyisolating said conductor from said mounting strap.

2. The receptacle of claim 1 wherein said body includes a detachableback plate defining a groove on its outer surface and wherein saidelectrical conductor comprises a metallic strip positioned in saidgroove.

3. The receptacle of claim 2 wherein said insulating means comprises astrip of insulating material positioned in said groove atop saidelectrical conductor.

4. The receptacle of claim 3 wherein said mounting strap is positionedin said groove atop said insulating material.

5. The receptacle of claim 4 wherein all of said body, back plate,electrical conductor, insulating means, and mounting strap are securedby locking means extending therethrough.

6. The receptacle of claim 5 wherein said electrical conductor definesan opening surrounding but spaced from said locking means.

7. The receptacle of claim 1 wherein said receptacle is duplex andwherein said electrical conductor comprises a bridging member having agrounding contact secured at substantially each end thereof.

8. The receptacle of claim 7 wherein said bridging member includes alaterally extending portion extending across the back of said body andincluding a forwardly bent portion positioned on the side of said bodyto form said grounding terminal means.

9. The receptacle of claim 1 wherein said receptacle is single anddefines a recess extending from its back surf-ace and wherein saidconductor is a metallic strip having said female contact mounted at oneend thereof, the other end being forwardly bent to lie in said recessand defining said grounding terminal means.

10. The receptacle of claim 9 wherein said strip includes a majorportion extending longitudinally of said body and an angled portionextending to said recess.

References Cited UNITED STATES PATENTS 1,591,707 7/1926 Harrington339-133 3,032,736 5/1962 Howells 33914 3,096,132 7/1963 Hubbell 339-44 X3,218,597 11/1965 Oehlerking et a1. 339l4 MARVIN A. CHAMPION, PrimaryExaminer.

P. A, CLIFFORD, Examiner.

1. AN ELECTRICAL GROUNDING RECEPTACLE WHICH COMPRISES: A BODY OFINSULATING MATERIAL DEFINING CHAMBERS THEREIN AND INCLUDING A FACEPORTION DEFINING OPENINGS COMMUNICATING WITH SAID CHAMBERS; A PLURALITYOF FEMALE ELECTRICAL CONTACTS WITHIN SAID CHAMBERS ALIGNED TO RECEIVEMALE CONTACTS INSERTED THROUGH SAID OPENINGS; GROUNDING TERMINAL MEANSON SAID BODY; AN ELECTRICAL CONDUCTOR JOINING SAID GROUNDING TERMINALMEANS AND AT LEAST ON OF SAID FEMALE ELECTRIAL CONTACTS; A METALLICMOUNTING STRAP ON SAID BODY; AND INSULATING MEANS FOR ELECTRICALLYISOLATING SAID CONDUCTOR FROM SAID MOUNTING STRAP.